Gastric secretory function
Gastric mucosa secretes gastric juice, which contained acidic and alkaline components, the main ones - is hydrochloric acid, pepsin, gastrin, internal factor (biermerin), macromolecular compounds and inorganic substances.
According to reports, parietal cells secrete hydrochloric acid concentration constant, which ranges from 140 to 160 mmol / l. At the time of formation of hydrochloric acid concentration of its higher. This initial acidity. Subsequently, under the influence of the alkaline substance occurs reduction in the concentration of hydrochloric acid in the stomach. Gastric acidity is defined by the acidic and alkaline components secret.
In the stomach, acid and alkaline secretions are constantly interacting components, wherein the neutralization and dilution of the hydrochloric acid.
Reducing the concentration of hydrochloric acid occurs as a result of ingestion of saliva and in cases duodenogastric reflux (while throwing duodenal contents into the stomach). Perhaps lowering the concentration of hydrochloric acid by the reverse penetration of hydrogen ions from the cavity of the stomach into the blood, especially inflammatory processes.
Hydrochloric acid has on the stomach contents bactericidal effect, increases motor activity of the stomach, but its most important function is to create an enabling environment for the proteolytic action of pepsin.
The main cells of the gastric glands produce inactive proteolytic enzyme pepsinogen, which in the presence of hydrochloric acid and converted into activated pepsin. The resulting pepsin accelerates (kataliziruet) conversion of the rest of pepsinogen. As the results of studies by different authors, in gastric juice, there are several classes of proteolytic enzymes hydrolases, united under the common name of pepsin.
Pepsin most active at pH 1,5-2,5. At pH 4,5 proteolytic activity of pepsin decreases, and in a medium having a pH 5,5 This enzyme is almost completely inactivated.
A small portion of the main pepsinogen falls cells of the gastric glands into the blood, and then in the urine. Full parallelism between pepsinogen gastric juice, Blood and urine there, However, determining the level of uropepsinogena has some clinical significance for evaluating gastric secretory function.
In normal gastric juice contained equal amounts of pepsin and gastrin. The role of gastrin is especially great under reduced acid production, at pH 3,0-3,2 gastrin stimulates acid-forming function of the stomach, allocation of pepsinogen, pancreatic juice and bile, enhances the motility of the intestines and activates the synthesis of insulin. Its synthetic derivative of pentagastrin is a powerful stimulus of gastric secretion.
The children in the gastric juice contains one enzyme - lipase, which at pH 5,5-7,9 able to digest lipids simple structure.
The main components of krupnomolekulyarnyh gastric juice is slime, which is mainly produced by the surface epithelium of the gastric mucosa. It protects the mucous membrane from mechanical, thermal and chemical damage and prevents autodigestion.
The source of soluble mucus are Mucocytes gastric glands. Slime, produced by cardiac and pyloric glands, is a complex compound mucoid substances with phosphates and bicarbonates. Mucus stomach has buffer properties: 1 Mr. mucin binds. 18 ml 0,1 n. hydrochloric acid, or 12 ml 0,1 n. alkali solution.
Thanks to the colloidal structure mucus absorbs a variety of substances, including enzyme pepsin. Contained in the mucus mukoitinsernaya acid and chondroitin, and their decay products have antiseptic properties.
Internal factor is a compound from the group glikozaminoproteoglikanov, It is produced by the parietal cells of the gastric glands. It established its participation in the resorption of cobalamin (Vitamin B12) in the gut. Absence of intrinsic factor in gastric juice leads to development B12– or anemia folievodefitsitnoy.
In addition to these, found in gastric juice and other biologically active macromolecular substance (anticoagulant action, lipotropic activity, erythropoietin) and proteins, эlektroforeticheskaya feature kotorыh similar harakteristikoy belkov Resurrection.
Of the inorganic compounds contained in the gastric juice xloridы, sodium, potassium, calcium. Neutral chlorides have a double origin: formed by neutralization of hydrochloric acid with sodium and secreted alkaline component consisting secretion. The level of potassium in the gastric juice above, and sodium and calcium enlarge, than serum. The concentration of sodium is in inverse proportion to the acidity of gastric juice. The level of secretion of calcium is directly proportional to the degree of isolation of pepsinogen. The concentration of potassium in the gastric juice constant.
The stomach has the ability to excrete some substances, normally allocates a small amount of products of nitrogen metabolism (This function is activated when azotemia), some dyes and medicaments (morphine, chloroform).
